The levinson stuff in the lexus is so/so, probably about on par with the bose. Pretty boring.
To get good sound in the car, you've really got to go aftermarket, and it is NOT cheap to get sound that an audiophile would find acceptable. I know because I've done it, and wasted a lot of money doing things over and over again when it didn't turn out right.
The most important thing (just like at home) is nailing the speakers and the acoustics. This is not trivial. Start with a good driver - this means a Dynaudio, Scan Speak, Morel, Seas, or Focal. If you are mounting drivers in the door, the door needs to become your speaker baffle/cabinet. It's got to be made extremely dead and non resonant, and internally damped. Ideally, you're going to want to mount your midrange and tweeter in the kick panel, which involves custom fiberglass enclosures.
The 2nd most important thing is making the car quieter. You've got to damp the entire interior of the car, trunk, etc. with dynamat or similar material. Doing this right will decrease the ambient noise by 10db or more easily. While it still won't be completely silent or quiet enough to hear the subtle inflections on solo violin playing pp, it'll get the job done.
The third most important thing is processing. You've got to RTA and EQ and do this in a relatively transparent way. A modded Behringer DCX is ideal, and with this you can drive the speakers actively as well and control the crossovers.
If you are lucky enough to find someone skilled enough to "get it" and do this work, it'll probably cost around $10k - $15k to do it right.
Beware most car audio people. Don't trust them unless you hear their work. They don't "get it" for the most part. Of course there are exceptions, but even "high profile" car audio dealers are not audiophiles.